PART 1: Notes on the 3D formation of the leading edge in a paraglider, using ripstop fabric.
PART 2: 3D-SHAPING PROGRAMMING ESTRATEGY
PART 3: Negative 3D-shaping
PART 4: A device for experimental study of deformations and wrinkles
In this PART 4 we propose a construction that can be used to study
experimentally the effect of different values of skin tension and
3D-cuts in the surfaces shapes.
The amounts of skin tension, the position and depth coefficient of the 3D cuts, can be determined from the following elements:
- Numeric values known previously (publications, data files).
- Previous experience.
- Geometry intuition.
- Calculations the geometrical and physical calculations, based on theories.
- Numeric models.
But it is a difficult task, and the final quality of the wing
will depend on to choose properly this values. In addition, the values
can change for each profile and for each wing shape. For this reason,
an additional element of study can be a "device" for studying
individual cells without the need to build an entire wing. We can
imagine two rigid profiles located next to one another in the position
of study. Between the two profiles, we can try different ripstop
surfaces of ripstop, which have been calculated with the help of a
program like LEparagliding, with different values of skin tension and
3D-shaping. The two profiles can be exactly the same, or slightly
different (to simulate changes in curvature at the leading edge). The
fact that they are completely rigid can simulate an ideal situation of
symmetrical forces on each side, which is not always the case, but
sufficient for the object of study.
An initial study could be to create two exactly equal and completely
parallel profiles, and to create different collections of panels with
3D cuts with amplified effect to observe the differences.
The device, described in the accompanying drawings, will be exposed to
a uniform wind and and observations will be visual and tactile (to
verify tissue pressure and stability) to detect areas of wrinkles,
deformations, high pressure or low pressure. From the analysis of
different test surfaces a conclusion will be reached on the best values
for a given profile. There is the possibility of mounting another pair
of rigid profiles symmetrically on the other side of the supports and
thus directly compare two identical cells but with different panels.
Figure 1. General concept of the device for experimental study of 3D curvatures and wrinkles.
Figure 2. Placement of panels on the profiles.
Figure 3. 3D view of the dispositive.
Ideally, the profiles to be studied should be on a real or 1/2 scale.
They will be cut into pieces of plywood that will be joined together by
3 or four threaded steel bars of 6 or 8 mm. A spacer washer will be
attached to one of the outer sides of the profile, which will be the
horizontal axis for adjusting the angle of attack. Here will be fixed a
wooden support that will continue in a metal tube, which will be the
vertical axis to face the wind. Alternatively, one or more fans may be
used in indoor installations. The vertical axis will be fixed to a firm
vertical support or tripod fixed to the ground.
